1. Field of the Invention
The present invention relates to gas emission sample containers for collecting gas emissions from motor vehicles.
2. State of the Art
Expandable, sealed containers or bags are employed for collecting and temporarily storing gas emissions from motor vehicles before the collected emissions are analyzed by suitable test equipment. Such containers are expandable to a predetermined volume to collect a known quantity of gaseous emissions.
Typically, a plurality of such containers, such as six containers, are connected through suitable conduits, valves, etc., to a test apparatus to collect separate quantities of gas emissions from a vehicle and from ambient atmosphere. The emission samples from a motor vehicle under test are collected in the sealed containers as the motor vehicle is operated according to a prescribed test schedule corresponding to various engine operating conditions.
The expandable containers include a fitting sealingly mounted in each container which is connected to the test apparatus to receive gas emissions from the vehicle under test. The fitting directs the gas emissions into the container for storage, as well as enabling the stored gas contents to be evacuated from the container for subsequent analysis. The fitting and the sealed container are made of a chemically inert material, such as a fluorinated carbon plastic, i.e., plastics sold under the registered trademarks TEFLON, KYNAR, and/or TEDLAR.
Accurate testing of gasses in a gas emission sample container requires the complete inflation of the container to a constant volume without internal dead spots as well as the complete evacuation of all gasses from the container. Specially designed, small, smooth fitting have been employed in gas emission sample containers to prevent the formation of internal dead spots during the evacuation of gas from such containers. In addition, hollow conduits or tubes having spaced apertures formed therein have been mounted within such containers and connected to the fitting to ensure complete and even inflation and evacuation of gas to and from the container, without stratification of the gas within the container.
It is also known to maintain the pressure of the gas emission sample container, when inflated to a known volume, at a constant pressure during storage and subsequent evacuation of gas therefrom. This prevents any change in volume of the gas due to pressure variations. However, the temperature of the gas may vary considerably due to the length of time between the storage of the gas in the container and its subsequent evacuation for testing as well as the length of the conduits between the motor vehicle under test, the storage container and the gas testing apparatus. Heat losses during the transfer of the gas from the motor vehicle to the storage container and from the storage container to the test apparatus as well as from the storage container itself can cause variations in the temperature and, thereby, the volume of gas and therefore a change in the percentage of the constituents of the gas leading to inaccurate test results.
Thus, it would be desirable to provide a gas emission sample container which maintains the temperature of gas stored therein at a constant temperature.